In this art, it is desirable that the proximity fuse does not detonate the warhead in cases which offer a direct hit on the target. Consequently, prior-art proposals have been put forward to give one and the same lobe for the emitted electromagnetic radiation the configuration of a planar disc with the normal directed in the flight path of the unit or alternatively the form of the circumferencial surface of a cone. It is further desirable in this art to employ short wave electromagnetic radiation - preferably within the IR range - such that unwieldy antenna clusters will be thus avoided. The drawback inherent in the prior-art IR radiation is that it is greatly reflected by the water droplets and ice crystals which are present in cloud and in precipitation. The conditions will become particularly unfavourable for proximity fuses of the above-mentioned disc or conical ray lobe under these circumstances. On target by-pass, or "near miss", but a minor faction of the radiation lobe will impinge upon the target, which entails that the emitted radiation must be given a high efficiency level in order that a reflected signal of sufficient strength be received. On passage through cloud or precipitation, the entire radiation lobe will be subject to "window effect" from the reflection of water droplets or ice crystals. As a result of the extent of the radiation lobe about the circumference of the launchable unit, and the high emitted effect, the reflected effect, i.e. the return dispersion, will be very high indeed.